This invention relates to construction materials and more particularly, to a new structural member.
Over the years, there have been several attempts to develop alternative construction materials to wood joists, rafters and studs. Even though the problems associated with wood, as a raw material, continue to increase in residential construction, wood remains the dominant structural material.
As world population and economic development increase, the demand for wood also increases, thereby placing significant pressures on our natural resources and other supplies of wood stock. The net result is a general increase in the price of wood. In addition, wood stock, as with other resources, experiences spot variations in price as a function of spot shortages caused by weather, transportation problems and other variables. Further, over the last several decades, the overall quality of wood stock has generally declined. The quality and price issues are even more dramatic for wood joists, that is, the structural members that extend horizontally between vertical walls and provide a subjacent for a floor or roof above the joist. Joist members are generally nominally, 2 inches thick, are nominally in a range of from six inches to 12 inches wide and are most often, ten feet and more in length. Thus, as the wood resource becomes more scarce, of generally lower quality and more expensive, larger wood structures, such as joists, which require high quality wood to provide the desired straightness over their lengths, are proportionally even more expensive.
In use, often to reduce costs, longer joists, for example, those over twelve feet, are fabricated from shorter pieces which are spliced together. Further, as with all wood products, wood joists are subject to damage from termites and other insects.
Several alternatives to the standard wood joist have been considered. For example, fabricated wood I-beams are commercially available from Trus Joist Corporation of Boise, Id. While such fabricated I-beams have the advantage of being manufactured to any length and having a predictable quality, such fabrications are relatively expensive.
Structural members made of steel are widely used in commercial office construction and are now beginning to be used in residential construction. Typically, steel structural members are used for wall studs to which a wall material, for example, wallboard, is attached. Rafters and ceiling joists are frequently integrated into a truss assembly. Such structural steel products are available from Clark-Cincinnati Steel Framing Systems of Cincinnati, Ohio.
A hybrid metal and wood I-beam structure is commercially available from Light Beam Inc. of Santa Monica, Calif. In this beam structure, a pair of sheet metal plates are clinched together to form an I-beam web section and wood members, for example, nominal 2.times.4 wood pieces, are attached to the web and form the top and bottom cords or flanges of the I-beam. Such a beam structure is fabricated from two identical sheet metal pieces which are attached with nails or other fasteners to the wood flanges. That structure again has some of the inherent disadvantages of an all wood beam, and has the further disadvantage of a relatively high cost to fabricate the hybrid sheet metal and wood structure.
Further, U.S. Pat. Nos. 3,342,007 and 2,049,926 illustrate different designs for a steel joist. However, in spite of the above, the use of substitutes for a standard wood joist in residential construction has been limited.
Consequently, there is a need for a substitute for the standard wood joist that does not have the limitations and disadvantages of known substitutes and provides a practical, higher quality joist structure for less cost.